1. FIELD OF THE INVENTION
This invention is directed to alkyd compositions containing a haloalkynyl biocidal compound, and especially a halopropargyl compound, and a transition metal drier. The invention is particularly directed to such compositions which have been stabilized to reduce the loss of biocidal activity. The invention is especially directed to the stabilization of alkyd compositions containing iodopropargyl carbamates, such as 3-iodo-2-propargylbutyl carbamate, and a cobalt drier by use of a chelating agent.
2. DESCRIPTION OF RELATED ART
Both exterior and interior surfaces and substrates of all types, when exposed to common environmental conditions, e.g. moisture, are prone to attack discoloration and various kinds of destruction by a variety of species of microorganisms, including fungi, algae, bacteria and protozoa. As a result, there has always been a great need for an effective and economical means to protect, for extended periods of time, both exterior and interior surfaces and various type substrates and commercial formulations from the deterioration and destruction caused by such microorganisms.
Materials which need protection with a suitable antimicrobial composition include stucco, concrete, stone, cementaceous surfaces, wood, caulking, sealants, leather, plastics, textiles, biodegradable compositions including such materials as paints and other coating formulations, surfactants, proteins, starch-based compositions, inks, emulsions and resins as well as numerous other materials and other substances which may be attacked by destructive microbes.
Wooden objects, in particular, are subject to degradation from a wide variety of natural pests, principally insects, such as carpenter ants, powder-post beetles and termites, marine borers and fungi. Fungi are particularly prevalent and are divided into three main groups, the brown rots, white rots and soft rots. Fortunately, a variety of compositions have been developed for treating wooden objects to retard the destructive effect of such pests.
An enormously wide variety of materials have been identified which, to various degrees, are effective in retarding or preventing the growth of, and accompanying destruction caused by, such microbes. Such biocidal compounds include halogenated compounds, organometallic compounds, quaternary ammonium compounds, phenolics, metallic salts, heterocyclic amines, formaldehyde donors, organo-sulfur compounds and the like.
One of the most common ways to apply such materials to wooden objects is to include them in a composition used to coat the object. The coating, in the form of paints, lacquers and varnishes, functions as a vehicle for the biocidal agent and acts as a barrier to the natural elements, such as sunlight and precipitation. A widely used coating formulation contains an alkyd resin, an oil, an optional solvent thinner and a drier. Such compositions form dried film coatings by a combination of solvent evaporation, resin oxidation and polymerization. The process is accelerated by the drier, which typically is a transition metal compound. Cobalt is the most widely used of the transition metals in such driers. To obtain a more uniform hardening, the cobalt drier is often combined with a lead compound or calcium/zirconium mixture.
One well-known class of biocides used in such coating compositions are those containing a halopropargyl moiety, and especially an iodopropargyl moiety. Such compounds are widely disclosed in the patent literature including U.S. Pat. No. 3,660,499; 3,923,870; 4,259,350; 4,592,773; 4,616,004 and 4,639,460 to name a few. Included within this class of compounds are the halopropargyl carbamates which are known primarily for their fungicidal activity. 3-iodo-2-propargyl butyl carbamate, hereinafter also referred to as IPBC, is one of the best known and probably the most widely used of the halopropargyl carbamate fungicides. IPBC is a highly active broad spectrum fungicide. In addition to its fungicidal activity, IPBC also has been associated with algaecidal activity. In this regard, Great Britain Patent 2,138,292 and U.S. Pat. Nos. 4,915,909 and 5,082,722 contain such disclosures.
Haloalkynyl compounds, including halopropargyl compounds, and especially the halopropargyl carbamates, are formulated with a variety of other ingredients in both aqueous and organic solvent mixtures to form coating materials. For various reasons, it is desired that these coating compositions maintain their biocidal activity for prolonged periods of time. Unfortunately, alkyd coating compositions containing transition metal driers have sometimes been observed to experience a progressive loss in such activity.
In particular, applicants have found that the gradual loss of biocidal activity in such alkyd coating formulations discussed above is caused by a reaction between the transition metal drier in these compositions and the haloalkynyl compounds.
Applicants have discovered that adding a chelating agent to such alkyd compositions formulated with a transition metal drier, particularly a cobalt drier, and a biocidal haloalkynyl compound, including specifically halopropargyl compounds such as IPBC, significantly retards the degradation of the biocidal agent. Use of the invention also helps to ameliorate other problems, such as the formation of lacrimators and the corrosion of metal containers caused by degradation of IPBC in solvent-based alkyd paint formulations.